I'd make a delrin nut. I used ordinary threaded rods in my first CNC and cut off a piece of the rod and made a tap out that and with the help of that tap I made delrin nuts. The nuts had really zero backlash for about a year, until I replaced all the threaded rods with ball screws. It served me well and the reason to replace was not backlash or accuracy issues, but simply speed and rigidity. The ball screws I am using now are 1605 and the rods were 12mm, which have a thread pitch of 1.75mm. Of course, the ballscrew/ballnut combo is much better, but on low budget threaded rods and custom made nuts are REALLY very good. Easy to replace the nuts, you can make a new one after a while, and it is really easy to make a tap if you have a piece to spare. There are many other methods of making a zero backlash nut out of delrin, and delrin is excellent for the purpose since it has low friction.

I would not make a rack out of Acetal (Delrin), I don't think it is good for that purpose, but it is suitable for making zero backlash nuts out of it.